Electric lamp.



790,4991 .PATENTED MAY 23, 1905. f M. w. HANKS.

' ELECTRIC LAMP.

APPLICATION FILE-D JULY 14, 1900- WITNESSES: Mi Enron I I Aria/Mr.

UNITED I STATES PATENT OFFICE.

MARSHALL W. HANKS, OF PITTSBURG, PENNSYLVANIA, ASSIGNOR TO GEORGE WESTINGHOUSE, OF PITTSBURG, PENNSYLVANIA.

ELECTRIC LAMP.

SPECIFICATION forming part of Letters Patent No. 790,499, dated May 23, 1905.

Application filed July 14:, 1900. Scrial'No. 23,659.

To all whom it may concern:

Be it known that I, MARSHALL W. HANKs, a citizen of the United States, residing at Pi ttsburg, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Electric Lamps, of which the following is a specification.

My invention relates to electric lamps of,

the type in which the light-giving body or glower is a conductor only when hot and the resistance of which decreases within limits as its. temperature increases.

The object of my invention is to provide a device which may serve the double purpose of heating the glower to a conducting temperature ,and thereafter acting as ballast to compensate for variations in the resistance of the glower.

It has heretofore been usual in practice to employ in lamps of this general character a coil of wire disposed adjacent to the glower and to connect such coil of wire to the supply-circuit in shunt to the glower and also to provide a cut-out device which operates when theglower becomes conductive to open the circuit of the heating-coil. It has also been usual to employ a resistance-body in series with the glower of such composition and di-' mensions as to maintain an approximately con-. stant current through it and the glower. It is obvious that the elimination of one of these elements would be desirable, since it would simplify the construction of the lamp, and I propose to substantially effect this result by utilizing a single device as both a heater and a ballast. The means for effecting this result are shown in the single figure of the accompanying drawing, in ,which 1 is a glower, and 2 the heater-ballast device, the latter being located in such close proximity to the glower as to insure a proper heating of the latter. The adjacent terminals of the glower and the heater-ballast are connected together and to one terminal of a suitable resistance 3, the other terminal of the resistance being connected to one terminal, 4,

.of a cut-out device 5, the other terminal, 6,

of this cut-out device being connected, by means of wires 7 and 8, to one of the supply-mains 9 and 10. The other terminal of the heater-ballast device 2 is connected to the supply-conductor 9 by means of a wire 11. The adjacent terminal of the glower is connected, by means of a wire 12, to one terminal of the coil 13 of the cut-out 5, the other terminal of the coil being connected by the wire 8 to the supply-conductor 10.

It will be observed that the circuit of the lamp is primarily through the conductors 8 and 7, the cut-out terminals, the resistance 3, heater 2, and wire 11 and that when the glower has been heated to conducting temperature the current will be conducted from main eonductor 10, through wire 8, coil 13, wire 12 and the glower, the heater-ballast 2, and'the wire 11, to main conductor 9. The cut-out will be instantly actuated by the coil 13, thus cutting the resistance 3 out of circuit and establishing a connection between the glower and the device 2. The device 2 must be made of such material that it will have the qualities necessary for a ballast resistancethat is to say, it must have a very marked positive temperature correctionand since the drop across the heater-ballast must be comparatively small Patented May 23, 1905.

in order that the glower may have a high efficiency it is desirable to include a resistance in series with the heater-ballast when it is acting as a heater in order to avoid such a rush of current under the line-pressure as to destroy it.

Inasmuch as various materials which have a positive temperature coefiicient are known in the art, I do not desire tolimit my invention to any specific material or to any specific form or arrangement of parts.

I claim as my invention 1. In an electric lamp of the type described, the combination with a glower,of a heater and a current-restraining device primarily connected in series with each other to operate independently of the glower and a circuit-controller for cutting the restraining device out of circuit and leaving the heater in series with the glower to act as a ballast therefor when the glower becomes conductive.

2. In an electric lamp of the type described, the combination with a glower, of a heaterballast device and a current-restraining device primarily connected in series with each other to operate independently of the glower and means for simultaneously cutting the restraining device out of circuit and leaving the heater-ballast device in series with the glower when the latter becomes conductive.

In testimony whereof I have hereunto subscribed my name this 9th day of July, 1900.

MARSHALL \V. HAN KS.

Witnesses:

HUGH A. CRooK, W. D. UPTEGRAFF. 

